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Metlon Corp. has eliminated downtime on its high-precision slitting machines thanks to a new Balston air dryer from Parker Hannifin.

Founded in 1947, Metlon Corp. provides slitting capabilities for a range of flexible materials on custom-built machines that can hold tolerances of ±0.001 in. and closer. The Cranston, RI, converter can slit rolls to 54 in. wide, with finished slit widths to 0.0078 in. — just three times the width of a human hair.

Metlon serves a number of industries from its 40,000-sq-ft plant, and in one typical application, gang-slits 278 ends of polyester film simultaneously to 0.0078 in. wide and winds each end on a separate traversed spool.

According to VP Wayne Etchells, “Because of the specialty work we do, we found it necessary to build all of our own slitters internally. We don't have any commercially purchased slitting machines in our plant.”

Compressed Air Sensors One of the competitive advantages of Metlon's slitting machines is extremely accurate registration in very narrow width slitting. For example, one job involved a 0.630-in.-wide film with 0.030-in.-wide numbers printed down the center. The customer required the film be slit to a final width of 0.040 in. and that the printed numbers be kept in the center of the finished width.

According to Etchells, the customer had asked a number of other companies to do this work and was told it was impossible. Metlon was successful because its machines are equipped with highly accurate edge guides that direct the material onto the machine.

Pneumatic edge guides from Coast Controls use air from the plant's main compressed air system. In the past, moisture built up in the air lines, causing valves and solenoids in the edge guides to rust. “It was a constant problem,” says Etchells. “At least every other day, one of the machines was down while we took apart and lubricated the valves. And in some cases, we had to replace the valves.” The maintenance took about one hour, at an estimated cost of $75/hr in lost productivity.

One possible solution to this problem was a refrigerated air system that dried the air as it cooled it. This was an expensive option, however, costing between $5,000 and $6,000, Etchells explains. Operating costs also would be high due to the electricity needed to run the system. Another option was a new type of compressed air dryer from the Filtration & Separation Div. of Parker Hannifin Corp. The Balston air dryers use membrane filter technology. “They guaranteed it would work, so we gave it a try,” reports Etchells.

Metlon installed a Balston Model 76-50-35 membrane air dryer, which produces a flow rate of 50 SCFM. Compressed air goes into the Balston system, but prior to entering the membrane drying portion of the system, the air passes through two high-efficiency coalescing filters. The filters remove water droplets and particulate contamination with an efficiency of 99.99% at 0.01 micron, according to Etchells. Next, the air passes into Balston dehydration membranes. These consist of bundles of hollow membrane fibers, each permeable only to water vapor. As the compressed air passes through the center of these fibers, water vapor permeates the walls of the fiber, and dry air exits from the other end. A small portion of the dry air (regeneration flow) is redirected along the length of the membrane fiber to carry away the moisture-laden air that surrounds it. This moisture-laden sweep gas is vented to the atmosphere, while the remainder of the dry air is piped to the pneumatic edge guides and other applications in the plant that use compressed air. The dryer delivers air with a dewpoint of 35 deg F.

Etchells adds the dryer is designed to operate continuously, and the only maintenance required is changing the prefilter cartridge once every 6-12 mo. Replacements cost about $40, and the time required to change the cartridge is approximately 5 min. No electrical supply is required to use these dryers, which makes them much less expensive to operate compared to refrigerants, says Etchells.

Another advantage over refrigerant air drying is that the Balston method does not produce condensate, reports Etchells, who says an average 100 CFM compressor system can produce up to 1,800 gal of oily condensate per year, adding a disposal cost to the operation as well.

The installation of the air dryer solved the problem Metlon was having with rust in the edge guides. “This new type of dryer was just what we needed to eliminate problems with water building up in compressed air lines. Since the day we installed it, we haven't had a single problem with rust,” says Etchells. “It has eliminated downtime. At an estimated rate of $75 per hour for the production rate of the machines, the dryer saves us more than $200 each week. At that rate, it paid for itself in just over three months.”

Air Filter Application In a core-cutting application for a customer in the electronics industry, Metlon was using nitrogen after the cores were cut to clean them of dust from the cutting process. “These cores are reels that eventually go into a Class-10 clean room, so they have to be perfectly free of dust,” Etchells says. “We were using compressed nitrogen to do this because compressed air, even though we had gotten it free of moisture with the air dryer, still had particulates. It wasn't clean enough to use for this job.” Metlon had compressed nitrogen delivered daily for this application at a cost of about $200/mo.

Parker Hannifin suggested an alternate solution — an air filter downstream from the air dryer that would trap the particulates. Metlon installed the A 15/80 downstream of the Balston air dryer in the line coming to the CoreTech cutting machine. “The filter removes 99.9 percent of the impurities from the compressed air, making it pure enough to clean those reels,” says Etchells. The company stopped its nitrogen deliveries completely, and those savings paid for the air filter in eight months.

“We have had no problems with either [the Balston air dryer or the air filter],” says Etchells. “They work just as advertised. Our compressed air system is now completely dry and clean at a very reasonable cost. And we gain at least three hours of production time each week by not having to shut down to clean rusted valves. To us, that is worth hundreds of dollars, making these products an excellent investment.”